Douglas X-3 Stiletto
     The slender, jet-powered X-3, built by Douglas Aircraft Company, Long Beach, California, tested such new materials as titanium and collected data on stability and control, pressure distribution, and flight loads. Because it was underpowered with an interim J34 engine, the X-3 failed to achieve the high speeds for which it was designed, but it pioneered in the use of titanium and contributed to the development of aircraft tire technology.  Following completion of contractor testing in 1953 and a brief Air Force evaluation in 1953-54, the lone X-3 aircraft (serial number 49-2892) was transferred to the National Advisory Committee for Aeronautics, with research pilot Joseph A. Walker of the High-Speed Flight Station (later: Dryden Flight Research Center) flying all 20 of its NACA research flights from 1954 to 1956.
      During Walker's tenth flight on October 27, 1954, he performed two abrupt, rudder-fixed aileron rolls at speeds of Mach 0.92 and 1.05 (0.92 and 1.05 times the speed of sound) that led to inertial roll coupling, causing him to diverge from the expected flight path. These two maneuvers, from which he fortunately was able to recover, yielded a wealth of valuable data on the (as yet not fully understood) phenomenon of inertial coupling. Together with data from other aircraft, such as the X-2 and the F-100, this helped the aeronautics community understand how to deal with the phenomenon of coupling dynamics.


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